1. Field of the Invention
This invention relates to microwave power splitters in general and more particularly to a power splitter having a small package size.
2. Description of the Prior Art
Power splitters have been made by forming transmission lines on microstrip structures using printed circuit boards. Power splitters have also been fabricated on ceramic substrates using screened on thick film conductors and dielectrics. In some applications, printed circuit board space is extremely limited with additional space just not available. It is desirable that the splitter be as small as possible while still having the proper impedance and not having excessive cross-talk noise. Printed circuit boards have a problem in power splitter applications in that the desired transmission line impedance can be hard to achieve in a small package size due to the low dielectric constant of the printed circuit board material. Ceramic materials have a higher dielectric constant and can achieve the same impedance transmission lines in a smaller size. Unfortunately, using a thick film process to fabricate a multilayered structure is difficult to manufacture on a repeatable and cost effective basis. Further, if the circuit lines are placed too close to each other in the ceramic package, excessive cross-talk noise can result.
While power splitters have been used, they have suffered from taking up excessive space, being difficult to manufacture and having excessive cross-talk noise. A current unmet need exists for a power splitter that is smaller, has low cross-talk noise and that can be easily fabricated.
It is a feature of the invention to provide a power splitter having a small package size that has repeatable electrical characteristics and low cross-talk noise.
Another feature of the invention is to provide a power splitter that includes a substrate having several layers. A resistor is formed on an outer layer. A first transmission line is formed by a first spiral shaped circuit line formed on an inner layer. A second transmission line is formed by a second spiral shaped circuit line formed on the inner layer. A ground plane is formed on another inner layer. Several vias extend between the layers and provide an electrical connection between the resistor, the ground plane and the circuit lines.
Another feature of the invention is to provide a power splitter that includes a low temperature co-fired ceramic (LTCC) substrate. The LTCC substrate has several layers. Electrical components such as transmission lines and resistors are integrated internally within the LTTC substrate. A pair of counter rotating circuit lines in a spiral are formed on a layer. The circuit lines are joined to input and output pads on layers above and below by vias. A resistor is connected between the output pads. The power splitter provides impedance matching and dividing functions. The LTCC substrate has electrically conductive vias extending therethrough. The vias are used to make electrical connections between layers of the LTCC substrate.
Another feature of the invention is to provide a power splitter that takes up less space and has improved electrical repeatability.
A further feature of the invention is to provide a method of manufacturing a miniature power splitter.
Another feature of the invention is to provide a power splitter with low cross-talk noise.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention.